The present invention relates to the electronics field, and more particularly, to a power limiting circuit for controlling the power of incandescent lamp not to overrun the predetermined power rating.
The conventional circuit for controlling or driving an incandescent lamp is commonly in an absence of the power limitation and protection. When an incandescent lamp is installed, if peripheral power that is greater than the power rating of the incandescent lamp is used by a mistake due to not knowing the type or power of the incandescent lamp, the increase of current will be induced and finally result in the burning out of lamps or wires and even the risk of fire.
At present, with respect to the above problems, some users provide a new technical solution that a coil is used to control the increase of the power of incandescent lamp. When the power of the incandescent lamp increases, the voltage across the coil will increase, which is fed back to a integrated control circuit, and the circuit will output a control signal to the related peripheral circuit to control the turnoff between the wire and the load so as to protect the incandescent lamp and avoid dangerous emergencies. This technique is widely used nowadays. However, the shortcoming is that the coil can be easily influenced by temperature, when the coil is connected to power supply, the current of the coil will increase, the voltage across the coil will increase due to the rapid increase of temperature, and thus the integrated control circuit would output a false signal to control the turnoff between the output and the load. The false signal will cause the light quenching of incandescent lamp. Moreover, the circuit is lack of temperature compensation circuit and fails to work stably.